The present invention relates to a tensile strength tester and, more particularly, to a tensile strength tester capable of measuring a tensile strength by pulling a screw member fitted in a base material out of the base material.
A resin molding, thin plate or similar article is often formed with screw portions and connected to another article by threaded engagement. To insure rigid connection, it is a common practice to implement each screw portion as an independent nut and connected to the base material by burying, welding, press fitting or similar technology. It is necessary to test the strength of connection between the screw member and the base member because the screw member should guarantee rigid connection between two articles. For the test, use is made of a tensile strength tester or tensile testing machine which exerts a tensile force on the screw member while fixing the base member in place, and measures the maximum connecting strength, i.e., the tensile strength of the base material and screw member in terms of a tensile force caused them to start separating from each other.
An Amsler type testing machine which is not portable is a typical conventional tensile strength tester. However, the problem with this type of tester is that preparation for measurement is troublesome and time-consuming while needing expertness. Further, the tester is a general purpose testing machine and therefore expensive. Moreover, it is difficult to measure the tensile strength of the base material and screw member at a work cite, e.g., the cite of injection molding. Particularly, the intention of the measurement of a tensile strength test is to improve the quality of products by feeding back the result of measurement to a production line. In this sense, a tester capable of readily measuring and testing the base material and screw member is desirable.
In light of the above, Japanese Patent Laid-Open Publication No. 3-125941, for example, discloses a tensile strength tester capable of being brought to a work cite and measuring or estimating the tensile strength of screw members with ease. However, the tester taught in this document has some problems left unsolved, as follows. The tester is too large and heavy to be easily handled by a person and not easily marketable. A portion where a rotatable member and a pulling member are connected is apt to become loose. The pulling member is not readily replaceable and obstructs easy maintenance of the tester. The tester operated by hand cannot stably measure tensile strength and should preferably be automated by use of, e.g., a motor.